This invention relates to the non-destructive analysis of standing and felled trees and poles, such as utility poles, and more particularly to generating two and three dimensional images of such trees that indicate their internal structure.
Trees and utility poles, such as telephone poles, are subject to various kinds of interior deteriorating and rotting conditions that are not evident from indicia outside of the tree or pole. Trees can undergo such internal rot for years, without noticeable symptoms to the leaves, bark or other observable structures. However, once the tree is cut down, and sawn up for use as lumber, paper, veneer, etc., the presence of large areas of rot greatly diminish the useability of the tree. In addition to rot, the presence of other internal structures, such as voids and knots, affects the uses to which a particular tree or tree section can be put. Thus there are many reasons to know the internal structure or condition of both standing and recently felled trees.
Owners and prospective purchasers of tracts of trees desire to know the general condition of the trees before they are purchased, or before efforts are made to log any significant percentage of such trees. Similarly, prospective purchasers of individual trees would like to be able to assess their condition before purchase. Arborists, or those responsible for the health of forests and trees would like to be able to assess the spread of any transmissible disorder of such trees, in order to better stem the movement of any such condition through a forest. Arborists are also interested in the type of rotting condition experienced by the tree, which may indicate the cause and treatment. Different types of rot are evidenced by different patterns of decay. Environmentalists who are interested in maintaining dead trees standing, such as for habitation by spotted owls and other animals, will be able to identify trees that are not worth logging, which may then be saved from logging because the lumber company would have no interest in felling a rotten tree.
Persons with militant anti-lumber attitudes have also been known to drive stainless steel spikes randomly into stands of trees. If such a spike is encountered by a saw during the felling or processing of such a tree, it can cause significant damage to equipment and injury to persons. The spikes can not be located by magnetic techniques, because stainless steel is not magnetically attractive.
At the level of an individual tree, if a lumber mill operator knows of the location inside a felled tree where there are rotting conditions, it is possible to make better use of the tree. For instance, if one were to know that the center of a tree is rotted, with the outside being in good shape, that tree could be dispatched to a veneer mill, which would xe2x80x9cpeelxe2x80x9d the outer, high quality wood from the tree, stopping when the rotted inner section is reached. In addition to rot, it is also helpful to know the locations of other internal non-uniformities, such as knots and voids, when sorting logs, or orienting logs for various mill operations. Such triage could be performed on whole trees, or on sections of trees.
Many of the foreging operations must be performed in the field on standing trees, far from any roads or mills. Thus, any equipment that is required to perform such operations must be small enough and light enough so that it can be carried to the standing tree by a single user. Further, it must be operable under battery or other portable power sources for a length of time that is long enough to make its use worth the effort of transporting it to the site.
Many problems similar to the foregoing also exist with standing wooden poles, such as utility poles, including telephone poles. Once in place and tied into a network, it is very expensive to remove and replace them. However, such poles do suffer from deterioration, such as rot and bug infestation, and must be replaced from time to time. Other types of wooden members that require knowledge about their internal condition include piers, pilings and scaffolds. These poles and wooden members are also often far from roads or are not readily accessible to heavy machinery.
Accordingly, for the foregoing reasons, there is a need for a relatively small, lightweight, long life apparatus that can generate a two dimensional image of the interior of a standing tree or pole or recently felled tree. There is also need for such a device that would operate quickly enough to give the operator an essentially immediate image of the tree or pole under inspection so that decisions of disposition of the tree or pole can be made in the field. There is further a need for a device that can readily be attached and removed from a tree or pole, to provide an image at different locations along a tree or pole , and further, for a device that can generate a three-dimensional representation of a standing tree or pole or recently felled tree in the field.
A preferred embodiment of the apparatus according to the invention is an ultrasonic computed tomography tree, pole, or log scanner. A plurality of ultrasonic transceivers (each of which can both transmit and receive ultrasonic impulses) are carried on a belt that is sized to encircle a typical tree or pole of the size to be examined. The belt includes a cinch or chain or other mechanical apparatus for engaging it very tightly around the circumference of the tree or pole to be examined. The transceivers are spaced around the tree or pole, and their mutual relative distances are known. Electronic circuitry is provided for energizing the transmitters in a known sequence. The signals that are received at each of the receivers are also collected and analyzed. Using computed tomographic techniques to analyze the time of arrival of the acoustic pulse that is first to arrive at each receiver, a signal processor generates a two dimensional image of a slice surface of the tree or pole at the locus of the belt. In addition to the time of arrival of the first wave to arrive, the attenuation of the energy of the first arriving wave also provides additional information that can be used in conjunction with the images that are based on the arrival time. The signal processing and transceiver controlling are performed by portable, lap-top type computers or smaller computing devices, such as PDAs, such as the Palm Pilot(trademark), sold by 3Com.
The transceivers may include spike-like engaging portions, that are pressed strongly into the bark of the tree to ensure good acoustic coupling. A radar apparatus is also optionally provided to help to determine the diameter of trees whose cross-sections diverge greatly from circular. The transceivers may be coupled to the signal processor over an infra-red channel. The battery power supply for the apparatus may be carried by the belt, or it may be separate.
According to another preferred embodiment of the invention, at least two, and preferably three belts, each belt carrying a plurality of transceivers, as discussed above, are spaced longitudinally along the section of tree or pole, for instance one to three feet apart from each other. In such an arrangement, again, pulses from individual transmitters are received at each of the receivers, and, based on computed tomographic analysis, the internal condition of the volumetric portion of the tree is determined over all three spatial dimensions.
Another preferred embodiment of the method of the invention is a method for the non-destructive examination of trees, poles, and logs, which includes the steps of acoustically coupling a plurality of ultrasonic transceivers to a tree or pole. The transmitters are pulsed according to a known order, and the signals from each transmitter are received at each of the receivers. The time of reception and the attenuation from the original signal is noted for each receiver. Using the time of arrival information, a two dimensional image is generated, by applying computed tomographic procedures to the data. The two dimensional image is displayed on a human perceptible device. In addition to the time of arrival data, the attenuation data may also be used to create an independent image or enhance the image of the internal structure of the tree, pole, or log. A similar method is conducted for the three dimensional data embodiment of the invention discussed above.